George Poinar Jr. Kenton L. Chambers Ron Buckley

EOËPIGYNIA BURmENSIS GEN. AND SP. NOV., AN EARLy CRETACEOUS EUDICOT
J. Bot. Res. Inst. Texas 1(1): 91 – 96. 2007
FLOWER (ANGIOSPERMAE) IN BURMESE AMBER
George Poinar Jr. Kenton L. Chambers
Department of Zoology Department of Botany and Plant Pathology
Oregon State University Oregon State University
Corvallis, Oregon 97331, U.S.A. Corvallis, Oregon 97331, U.S.A.
Ron Buckley
9635 Sumpter Road
Florence, Kentucky 41042-8355, U.S.A.
abstract
Eoëpigynia burmensis gen. & sp. nov. is described from Early Cretaceous Burmese amber. The genus is characterized by small, perfect,
actinomorphic flowers possessing a perianth with a single series of basally connate sepals, four distinct equal petals, four included
stamens alternate with the petals, an inferior ovary, a single style with a bilobed stigma, and triaperturate pollen. Flowers with similar
morphology occur in the family Cornaceae.
key words: Burma, amber, eudicot flower, Early Cretaceous, Cornaceae
resumen
Eoëpigynia burmensis gen. & sp. nov. se describe del ámbar birmano del Cretácico temprano. El género se caracteriza por tener flores
pequeñas, perfectas, actinomórficas que tienen un perianto con una serie sencilla de sépalos connados en la base, cuatro pétalos independientes
iguales, cuatro estambres inclusos alternando con los pétalos, un ovario ínfero, un estilo simple con estigma bilobulado, y
polen triaperturado. Existen flores con una morfología semejante en la familia Cornaceae.
introduction
Burmese amber has an interesting past dating back to AD 100 when an amber trade route was established
with China. The first Europeans visited the mines in 1836 but it was not until 1896 that the amber was
noted to contain insect remains. From AD 100 until 1936, the Burmese amber mines supplied amber to
various parts of the world (Chhibber 1934). In 2001, a new amber mine was excavated in the Hukawng
Valley, southwest of Maingkhwan in the state of Kachin (26º20'N, 96º36'E) (Poinar et al. 2005). This new
amber site, known as the Noije Bum 2001 Summit Site, was dated to the Upper Albian (100 to 105 mybp)
of the Early Cretaceous (Cruickshank & Ko 2003).
The Early Cretaceous age of amber from the Noije Bum 2001 Summit Site as determined by Cruickshank
and Ko (2003) is supported by primitive insects from this deposit. For example, a bee was discovered still
possessing characters of sphecid wasps, the group considered ancestral to bees (Poinar & Danforth 2006).
An elcanid grasshopper was also found at this site, representing a group (Elcanoidea) that first appeared in
the Early Permian and continued only to the mid-Cretaceous (Poinar et al. 2007). Thus, both paleontological
data and inclusions in the amber support an Early Cretaceous age for deposits from the Noije Bum 2001
Summit Site.
Nuclear magnetic resonance (NMR) spectra of amber samples taken from that locality indicate an araucarian
(possibly Agathis) source of the amber (Lambert & Wu, unpublished data 2002). While insects are
dominant, the deposits have revealed some very interesting plant fossils, including a unisexual flower with
affinities to the family Monimiaceae (Poinar & Chambers 2005) and two early bambusoid grasses (Poinar
2004). In the present paper, we describe a bisexual flower, provisionally assigned to the family Cornaceae,
from the Noije Bum 2001 Summit Site.

92 Journal of the Botanical Research Institute of Texas 1(1)
materials and methods
The flower is complete and well-preserved. One of the petals shows some evidence of insect damage, and
fungal hyphae are associated with one of the anthers. The flower was in anthesis at entombment, and pollen
grains occur on and adjacent to the anthers as well as on the stigma. The piece of amber containing the flower
is square, measuring 5 mm in length by 5 mm in width by 1.5 mm deep. Examination and photographs were
made with a Nikon stereoscopic microscope SMZ-10 R at 80 × and a Nikon Optiphot microscope at 800×.
description
Eoëpigynia Poinar, Chambers & Buckley, gen. nov. type species: Eoëpigynia burmensis Poinar, Chambers & Buckley, sp. nov.
Diagnosis.—Flowers small, bisexual, regular, epigynous; perianth tetramerous; calyx comprising a short
crown (gamosepalous) at summit of ovary, sepal lobes incised, number uncertain; petals 4, separate, valvate,
regular; stamens 4, free to base, in a single whorl, alternating with the petals, filaments linear, anthers introse,
dorsifixed; pollen shed singly, pollen grains triaperturate (possibly tricolporate with thickened exine
adjacent to colpi); gynoecium syncarpous, ovary inferior, style 1, stigma bilobed, pericarp wall thick-textured
at anthesis, fruit type unknown; presence of floral disc not determinable.
Eoëpigynia burmensis Poinar, Chambers & Buckley, sp. nov. (Figs. 1–2). type: myanmar (burma): kachin: northern
Myanmar, amber mine in the Hukawng Valley, SW of Maingkhwan, (26º20´N, 96º36´E), Aug 2005, Buckley s.n. (holotype: perfect
flower (accession # ab 214) deposited in the collection of Ron Buckley, Florence, Kentucky 41042-8355, U.S.A.).
Description.—Flower bisexual, glabrous, length 1.5 mm; no free hypanthium evident; calyx lobes with
incised margins, greatest length of calyx 0.34 mm; petals lanceolate-ovate, margins abaxially recurved, up
to 0.95 mm long, 0.34 mm wide; stamens with ovoid anthers up to 0.15 mm long, filaments 0.54–0.61 mm
long; stigma at level of anthers, estimated length of style 0.55 mm; length of ovary 0.54 mm; width of ovary
0.39 mm; diameter of pollen grains, 12–14 µm.
Etymology.—Genus name from the Greek “eos” dawn, “epi-“ upon, and “gyne” female, from the age and
the relation of the floral perianth to the ovary. Species named for the country of origin of the fossil.
discussion
Certain structures that would be helpful in the placement of Eoëpigynia, for example the presence of a floral
disc, could not be observed due to the fossil’s orientation in the amber. However, it was possible to view the
flower from both sides to verify the characteristics described here. Based on its floral features, Eoëpigynia
(Figs. 1, 2) represents a core eudicot that can provisionally be assigned to the family Cornaceae sensu lato,
in the basal asterid order Cornales. The phylogenetic position of Cornales as sister to all the remaining
asterids (perhaps excluding Ericales) is well confirmed by molecular studies (Stevens 2001 onwards; Hilu
et al. 2003; Judd & Olmstead 2004; Bremer et al. 2004). The perfect flower, inferior ovary, compound style,
4-merous perianth and androecium, and possibly tricolporate pollen of our fossil are most similar to the
modern genus Cornus (see illustrations in Wangerin 1910; Judd et al. 1999). The pollen of the fossil may be
of particular importance in this placement. In an equatorial optical section (Fig. 1D) three distinct paired
thickenings are seen in the exine marking what we assume are the three colpi (we could not focus our instrument
clearly on a pore at this spot). This pattern is strongly reminiscent of SEM equatorial transections
of Cornus pollen illustrated by Ferguson (1977), e.g. his figure 2c of thickened endexine in this area in C.
volkensii, as well as his figures 4d of C. disciflora and 6c of Curtisia dentata. Because of the pollen orientation
in the amber, we were unable to observe a pore face-on, where the characteristic H-shaped endoaperture
thinning pattern of Cornaceae/Nyssaceae might be seen (Erdtman 1966; Ferguson 1977). The pollen grains
of Eoëpigynia are smaller than in most of the types defined by Ferguson (1977) but are within the range of
his Curtisia-type, described as 12–20 × 12–17 μm (p. 6). One might speculate that small pollen are related
adaptively to the small size of pollinating insects of that period, for example the 2 mm-long bee recently
described from Burmese amber by Poinar and Danforth (2006).

Poinar et al., Eoëpigynia burmensis, an Early Cretaceous eudicot flower 93
Fig. 1. Eoëpigynia burmensis in Burmese amber. A. One side of flower. Scale bar = 0.34 mm. B. Opposite side of flower. Scale bar = 0.34 mm. C. Stamen:
anther covered with triangular pollen mass held together by fungal hyphae. Scale bar = 0.17 mm. D. Pollen grains on anther. Insert shows individual
pollen grain (arrows indicate aperture areas surrounded by thickened exine. Scale bar = 18 µm.

94 Journal of the Botanical Research Institute of Texas 1(1)
Fig. 2. Flower of Eoëpigynia burmensis in Burmese amber. Anther on right as described in Fig. 1C. Scale bar = 0.34 mm.
The generic makeup of Cornales, as well as family Cornaceae, has been reexamined in recent molecular
phylogenetic studies (Xiang et al. 1998; Fan & Xiang 2003; Hilu et al. 2003; Judd & Olmstead 2004). It is
proposed that Cornaceae be limited to two genera, Cornus and Alangium, and that other genera formerly
assigned here be segregated to families Nyssaceae, Mastixiaceae, and Grubbiaceae. At the ordinal level, the
once widely separated families Loasaceae and Hydrangeaceae are to be included in Cornales. If Eoëpigynia is
placed in the larger context of this basal asterid clade, it shows that a simplified epigynous flower, with a single
style, 4-merous perianth parts, and four stamens, arose early in the differentiation of this evolutionary line.
As pointed out by Gustafsson and Albert (1999), epigyny is not a recent phenomenon. Examples were
found by Friis et al. (1994) in Early Cretaceous sediments in Portugal, originally dated as Valanginian or
Hauterivian but now reassigned to the early Albian (Heimhofer et al. 2005). A probable relationship to
Chloranthaceae has been established (Eklund et al. 2004). Phylogenetic studies have also shown that the
evolution of ovary position has been dynamic, with at least 64 changes from hypogyny to epigyny but only
24 changes in the opposite direction (Gustafsson & Albert 1999; Soltis et al. 2003). In neither of these papers
are Cornales specifically discussed, however. Modern Cornales are well represented in the Southeast Asian
flora, with Cornus itself having a circumpolar Northern Hemisphere distribution (Wangerin 1910; Xiang
et al. 2005). Reference fossils (fruit stones) attributed to the Cornelian-Cherry line of Cornus in the latter
paper are taken from the careful review by Eyde (1988) and are Eocene or younger in age.
In studies using molecular phylogenetic dating methods with known fossil reference points (Bremer et
al. 2004; Anderson et al. 2005), the Early Coniacian (88 mybp) cornalean genus Hironoia (Takahashi et al.
2002) has been used. Based on these papers, the age of the stem group asterids may be ca. 128 mybp, the
Cornales and Ericales diverging soon afterwards (Stevens 2001 onwards). Anderson et al. (2005) place the
separation of Cornales from remaining asterids at ca. 109 mybp. The reference fossil Hironoia consists of

Poinar et al., Eoëpigynia burmensis, an Early Cretaceous eudicot flower 95
three-dimensionally preserved drupes, with characters of the endocarp wall and dehiscence valves synapomorphic
with the genera Nyssa and mastixia. However, it could not be placed with certainty in one or the
other genus. Another known cornalean fossil is Tylerianthus from the Upper Cretaceous Turonian Period,
ca. 90 mybp (Gandolfo et al. 1998; Crepet et al. 2004), with affinities to the Hydrangeaceae. The putative
cornacean fossil Eoëpigynia would extend the age of the clade, if used in similar dating studies. It would be
well to note, however, that its generalized floral morphology would allow possible placement of this fossil in
other epigynous clades of core eudicots as well, including Saxifragales, Myrtales and Asterales. Its similarity
to Cornaceae, although highly suggestive, is not fully diagnostic of the proposed relationship. We know of
no other fossil flower from the Cretaceous with the floral syndrome of this specimen.
acknowledgments
The authors thank Elmar Robbrecht for comments comparing the fossil to members of the family Rubiaceae
and Roberta Poinar for reading earlier drafts. The helpful comments by reviewers Steven R. Manchester and
James A. Doyle are much appreciated.
references
anderson, C.L., K. breMer, and E.M. Friis. 2005. Dating phylogenetically basal eudicots using rbcL sequences and
multiple fossil reference points. Amer. J. Bot. 92:1737–1748.
breMer, K., E.M. Friis, and B. breMer. 2004. Molecular phylogenetic dating of asterid flowering plants shows Early
Cretaceous diversification. Syst. Biol. 53:496–505.
CHHibber, H.L. 1934. The mineral resources of Burma. Macmillan & Company, London.
CrepeT, W.L., K.C. nixon, and M.A. gandolFo. 2004. Fossil evidence and phylogeny: the age of major angiosperm clades
based on mesofossil and macrofossil evidence from Cretaceous deposits. Amer. J. Bot. 91:1666–1682.
CruiCksHank, R.D. and K. ko. 2003. Geology of an amber locality in the Hukawng Valley, northern Myanmar. J.
Asian Earth Sci. 21:441–455.
eklund, H., J.A. doyle, and P.S. Herendeen. 2004. Morphological phylogenetic analysis of living and fossil Chloranthaceae.
Int. J. Plant Sci. 165:107–151.
erdTMan, G. 1966. Pollen morphology and plant taxonomy. Angiosperms. Hafner Publishing Company, New
York.
eyde, R.H. 1988. Comprehending Cornus: Puzzles and progress in the systematics of dogwoods. Bot. Rev.
54:233–351.
Fan, C. and Q-Y. xiang. 2003. Phylogenetic analyses of Cornales based on 26S rRNA and combined 26S rDNAmatK-rbcL
sequence data. Amer. J. Bot. 90:1357–1372.
Ferguson, I.K. 1977. Cornaceae. World pollen and spore flora 6:1–34. Stockholm.
Friis, E.M., K.R. pedersen, and P.R. Crane. 1994. Angiosperm floral structures from the Early Cretaceous of Portugal.
Pl. Syst. Evol. [Suppl.] 8:31–49.
gandolFo, M.A., K.C. nixon, and W.L. CrepeT. 1998. Tylerianthus crossmanensis gen. et sp. nov (aff. Hydrangeaceae)
from the Upper Cretaceous of New Jersey. Amer. J. Bot. 85:376–386.
gusTaFsson, M.H.G. and V.A. alberT. 1999. Inferior ovaries and angiosperm diversification. In: P.M. Hollingsworth,
R.M. Bateman and R.J. Gornall, eds. Molecular systematics and plant evolution. Taylor & Francis, London. Pp.
403–431.
HeiMHoFer, U., P.A. HoCHuli, S. burla, J.M.L. dinis, and H. weisserT. 2005. Timing of Early Cretaceous angiosperm diversification
and possible links to major paleoenvironmental change. Geology 33:141–144.
Hilu, K.W., T. borsCH, A. Müller, D.E. solTis, P.S. solTis, V. savolainen, M.W. CHase, M.P. powell, L.A. aliCe, R. evans, H. sauqueT,
C. neinHuis, T.A.B. sloTTa, J.G. roHwer, C.S. CaMpbell, and L.W. CHaTrou. 2003. Angiosperm phylogeny based on
matK sequence information. Amer. J. Bot. 90:1758–1776.
Judd, W.S., C.S. CaMpbell, E.A. kellogg, and P.F. sTevens. 1999. Plant systematics: a phylogenetic approach. Sinauer
Associates, Sunderland, MA.

96 Journal of the Botanical Research Institute of Texas 1(1)
Judd, W.S. and R.G. olMsTead. 2004. A survey of tricolpate (eudicot) phylogenetic relationships. Amer. J. Bot.
91:1627–1644.
poinar, Jr., G.O. 2004. Programinis burmitis gen. et sp. nov., and P. laminatus sp. nov., Early Cretaceous grass-like
monocots in Burmese amber. Austral. Syst. Bot. 17:497–504.
poinar, Jr., G.O., R. buCkley, and A. brown. 2005. The secrets of Burmese amber. Mid Amer. Paleont. Soc. 29:20–29.
poinar Jr., G.O. and K.L. CHaMbers. 2005. Palaeoanthella huangii gen. and sp. nov., an Early Cretaceous flower (Angiospermae)
in Burmese amber. Sida 21:2087–2092.
poinar, Jr., G.O. and B.N. danForTH. 2006. A fossil bee from Early Cretaceous amber. Science 314:614.
poinar, Jr., G.O., A.V. goroCHov, and R. buCkley. 2007. Longioculus burmensis, n. gen., n. sp. (Orthoptera: Elcanidae)
in Burmese amber. Proc. Entomol. Soc. Wash. 109:649–655.
solTis, D.E., M. FisHbein, and R.K. kuzoFF. 2003. Reevaluating the evolution of epigyny: data from phylogenetics and
floral ontogeny. Int. J. Plant Sci. 164(S5):S251–S264.
sTevens, P.F. (2001 onwards). Angiosperm Phylogeny Website. Version 7, May 2006 [and more or less continuously
updated since]. http://www.mobot.org/MOBOT/research/APweb
TakaHasHi, M, P.R. Crane, and S.R. ManCHesTer. 2003. Hironoia fusiformis gen. et sp. nov.: a cornalean fruit from the
Kamikitaba locality (Upper Cretaceous, Lower Coniacian) in northeastern Japan. J. Plant Res. 115:463–473.
wangerin, W. 1910. Cornaceae. In: A. Engler, Das Pflanzenreich. IV. 229:1–110.
waTson, L. and M.J. dallwiTz.1992 onwards. The families of flowering plants: descriptions, illustrations, identification,
and information retrieval. Version: 29th July 2006. http://delta-intkey.com
xiang, Q-Y., D.E. solTis, and P.S. solTis. 1998. Phylogenetic relationships of Cornaceae and close relatives inferred
from matK and rbcL sequences. Amer. J. Bot. 85:285–297.
xiang, Q-Y., S.R. ManCHesTer, D.T. THoMas, W. zHang, and C. Fan. 2005. Phylogeny, biogeography, and molecular dating
of Cornelian Cherries (Cornus, Cornaceae): tracking Tertiary plant migration. Evolution 59:1685–1700.